Article 110 OF the National Electrical Code (NEC) covers general requirements for the examination and approval, installation and use, access to and spaces about electrical conductors and equipment; enclosures intended for personnel entry; and tunnel installations. The scope does not come close to mentioning the vast number of topics in Article 110. Some of the other subjects covered there include voltages, conductors, wiring integrity, interrupting rating, selective coordination, mechanical execution of work, mounting and cooling of electrical equipment, arc-flash hazard warning, markings, available fault current, spaces about electrical equipment, and enclosure types. There are five parts in Article 110, with 26 main sections in the first two parts. 


Part I contains general provisions, and Part II contains provisions for electrical systems rated 600 volts (V), nominal, or less. Quite a few of these sections contain subsections. Subsection 110.26, Spaces About Electrical Equipment, contains six subsections (A–F), and half of those are subdivided even more.


The second subsection in 110.26 is “Clear Spaces.” The first sentence in 110.26(B) states the working space required by this section shall not be used for storage. This is similar to the first sentence of 110.26, which states access and working space has to be provided and maintained. Unfortunately, there are instances in which working space is provided when the building is constructed, but, after it is occupied, it becomes a storage space (see Figure 1).


The second sentence in 110.26(B) mentions live parts that are normally enclosed, not those that are normally exposed. When normally enclosed live parts are exposed for inspection or servicing, the working space—if in a passageway or general open space—shall be suitably guarded [110.26(B)].


While electrical equipment, such as switchboards and panelboards, can be located in dedicated rooms, such as electrical equipment rooms, it is not mandatory. Often, panelboards are located in passageways and general open spaces. Although live parts have to be guarded, the second sentence in 110.26(B) states, when normally enclosed live parts are exposed, the working space has to be guarded. It does not state to guard the live parts. When energized conductors and circuit parts are exposed because of someone inspecting or servicing the electrical equipment, it is vital to keep the working space suitably guarded to keep unqualified workers away from the live parts and away from the person working on the live parts.


Article 100 defines “guarded” as covered, shielded, fenced, enclosed or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats or platforms to remove the likelihood of approach or contact by people or objects to a point of danger (see Figure 2).


As 90.1(A) states, the NEC is not intended as a design specification, but aspects must be considered when designing a building and electrical system.


The entrance to and egress from working space must be considered in the design stage. Requirements pertaining to entrance and egress is covered in 110.26(C)(1) through (3). 


The first requirement in 110.26(C) is simple: at least one entrance of sufficient area shall be provided to give access to and egress from working space about electrical equipment. Unless the electrical equipment is large equipment—which is covered in the next section—there is no minimum width or height for the opening for the entrance to the working space.


Some electrical equipment is required to be readily accessible. In accordance with 230.70(A)(1), the service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside the nearest the point of entrance of the service conductors. Article 100 defines “readily accessible” as capable of being reached quickly for operation, renewal or inspections without requiring those to whom ready access is requisite to actions, such as to use tools, to climb over or remove obstacles, or resort to portable ladders and so forth.


Not all electrical equipment is required to be readily accessible. As long as it is not large, access to the equipment could be through a 30-by-30-inch opening with a permanent ladder. Although there is no minimum dimension for the entrance, it is required to comply with the minimum dimensions for the electrical equipment’s working space.


Section 110.26(C)(2) pertains to large electrical equipment containing overcurrent, switching or control devices. Examples include switchboards, switchgear and motor control centers. The only three places the NEC mentions the term “large equipment” is 110.26(C)(2), 110.33(A)(1) and 314.24(B)(1).


Large equipment in 110.26(C)(2) means equipment rated 1,200 amperes (A) or more and more than 6 feet wide. Because these requirements are in Part II of Article 110, the equipment has to be rated 600V, nominal, or less. A switchboard may be rated 1,200A or more, but if it is not more than 6 feet wide, 110.26(C)(2) does not apply. Likewise, a switchboard may be more than 6 feet wide, but if it is not rated 1,200A or more, 110.26(C)(2) does not apply.


For electrical equipment meeting all of these parameters, there has to be at least two entrances. There shall be one entrance (or more specifically, entrance to and egress from) at each end of the working space.


For example, a 2,000A, three-phase, 480Y/277V switchboard will be installed in an electrical room. The width of the room is 10 feet, and the width of the switchboard is 8 feet. In accordance with 110.26(A)(2), the working space width shall be the width of the equipment (8 feet). Across from the front of the switchboard is a concrete block wall. In accordance with Table 110.26(A)(1), the depth of working space or minimum clear distance in front of the switchboard shall be 3 feet, 6 inches. The actual clear distance in front of this switchboard is 4 feet. With this installation, there shall be one entrance to and egress from the required working space at each end of the working space (see Figure 3).


For electrical equipment that does not meet the parameters of large equipment, the entrance just has to be of sufficient area to give access to and egress from working space. With large equipment, there are minimum dimensions for the entrances. Each entrance to and egress from the required working space shall be at least 2 feet wide and 61⁄2 feet high. This is the minimum size opening into and out of the working space; the actual opening can be larger.


For example, the entrances into the electrical room in Figure 4 are through doors that can be locked to keep out unqualified people. The size of each door is 3 feet wide by 6 feet, 8 inches high.


Note that this section is not saying the entrance to and egress from is for the room where the large electrical equipment is located. Section 110.26(A)(1) says the entrance to and egress from is for the required working space. If large electrical equipment is located in a large open space, there may not even be any entrances near the electrical equipment.


For example, a 1,200A, three-phase, 480Y/277V switchboard will be installed in a large open area in a factory. The width of the switchboard is 7 feet. There are no live or grounded parts on the other side of the working space. In accordance with Table 110.26(A)(1), the depth of working space in front of the switchboard shall be 3 feet. The actual clear distance in front of this switchboard is 4 feet. With this installation, there shall be one entrance to and egress from the required working space at each end of the working space.


Under specific conditions, a single entrance to and egress from the required working space for large equipment shall be permitted. These conditions will be discussed in next month’s column.